ia64/linux-2.6.18-xen.hg

view lib/sort.c @ 782:9ab1c319531f

merge with linux-2.6.18-xen.hg
author Isaku Yamahata <yamahata@valinux.co.jp>
date Wed Jan 28 13:07:23 2009 +0900 (2009-01-28)
parents 831230e53067
children
line source
1 /*
2 * A fast, small, non-recursive O(nlog n) sort for the Linux kernel
3 *
4 * Jan 23 2005 Matt Mackall <mpm@selenic.com>
5 */
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/sort.h>
10 #include <linux/slab.h>
12 static void u32_swap(void *a, void *b, int size)
13 {
14 u32 t = *(u32 *)a;
15 *(u32 *)a = *(u32 *)b;
16 *(u32 *)b = t;
17 }
19 static void generic_swap(void *a, void *b, int size)
20 {
21 char t;
23 do {
24 t = *(char *)a;
25 *(char *)a++ = *(char *)b;
26 *(char *)b++ = t;
27 } while (--size > 0);
28 }
30 /*
31 * sort - sort an array of elements
32 * @base: pointer to data to sort
33 * @num: number of elements
34 * @size: size of each element
35 * @cmp: pointer to comparison function
36 * @swap: pointer to swap function or NULL
37 *
38 * This function does a heapsort on the given array. You may provide a
39 * swap function optimized to your element type.
40 *
41 * Sorting time is O(n log n) both on average and worst-case. While
42 * qsort is about 20% faster on average, it suffers from exploitable
43 * O(n*n) worst-case behavior and extra memory requirements that make
44 * it less suitable for kernel use.
45 */
47 void sort(void *base, size_t num, size_t size,
48 int (*cmp)(const void *, const void *),
49 void (*swap)(void *, void *, int size))
50 {
51 /* pre-scale counters for performance */
52 int i = (num/2) * size, n = num * size, c, r;
54 if (!swap)
55 swap = (size == 4 ? u32_swap : generic_swap);
57 /* heapify */
58 for ( ; i >= 0; i -= size) {
59 for (r = i; r * 2 < n; r = c) {
60 c = r * 2;
61 if (c < n - size && cmp(base + c, base + c + size) < 0)
62 c += size;
63 if (cmp(base + r, base + c) >= 0)
64 break;
65 swap(base + r, base + c, size);
66 }
67 }
69 /* sort */
70 for (i = n - size; i >= 0; i -= size) {
71 swap(base, base + i, size);
72 for (r = 0; r * 2 < i; r = c) {
73 c = r * 2;
74 if (c < i - size && cmp(base + c, base + c + size) < 0)
75 c += size;
76 if (cmp(base + r, base + c) >= 0)
77 break;
78 swap(base + r, base + c, size);
79 }
80 }
81 }
83 EXPORT_SYMBOL(sort);
85 #if 0
86 /* a simple boot-time regression test */
88 int cmpint(const void *a, const void *b)
89 {
90 return *(int *)a - *(int *)b;
91 }
93 static int sort_test(void)
94 {
95 int *a, i, r = 1;
97 a = kmalloc(1000 * sizeof(int), GFP_KERNEL);
98 BUG_ON(!a);
100 printk("testing sort()\n");
102 for (i = 0; i < 1000; i++) {
103 r = (r * 725861) % 6599;
104 a[i] = r;
105 }
107 sort(a, 1000, sizeof(int), cmpint, NULL);
109 for (i = 0; i < 999; i++)
110 if (a[i] > a[i+1]) {
111 printk("sort() failed!\n");
112 break;
113 }
115 kfree(a);
117 return 0;
118 }
120 module_init(sort_test);
121 #endif